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10 Amps @ 90 Vdc with the TL783

David Poston
Intellectual 315 points
Other Parts Discussed in Thread: TL783, UC3844

I am working on a DC motor control and I would like to know if the TL783 can be used. I need 90 Vdc at 10 amps maximum current. I see in the data sheet (Fig. 19 & 20) that the TL783 can be used as a shunt regulator with transistors to boost current. I have a Toshiba MG15H1AL1 IGBT transistor module rated at 600 V @ 150 A. that I would like to use as either a series losser element or shunt element. I have a power supply made with a 1100 watt transformer  and a Toshiba 106L2C43A full wave rectifier rated at 600 V @ 160 A. I have a 3900 µF capacitor for a filter.

My no load voltage is 140 Vdc. With a 24 Ω load it drops to 123 Vdc @ 5.6 A with 10 Vpp ripple @ 120 Hz. This approximately the load my 1 HP DC motor would draw.

  • 0
    TI__Guru**** 152966 points

    David,

    This could be done. However the power efficiency will be poor and substantial heat sinks will be needed.
    Figure 19 in data sheet shows a current boost by turning on the transistors when the TL783 draws significant current.

    The voltage across the TL783 must not exceed 125V at any time including faults.

  • 0 in reply to Ron Michallick
    Intellectual 315 points

    Thank you for the reply Ron!

    Is there a switching type IC available that I could use instead of the TL783? And would it be possible to use my IGBT module with it? I found these parts in an old CNC machine tool at the machine shop where I work. My objective is to mount a treadmill motor on a small drill press in place of the fixed speed AC motor. Heat sinks are not too much of a problem, I have some CPU heat sinks with fans. I will probably use an old PC case as a chassis.

    Perhaps I could do it the old fashioned way and build a shunt regulator out of discrete components. If I do, is there a good voltage reference IC I could use in place of a zener diode?

  • 0 in reply to David Poston
    TI__Guru**** 152966 points

    David,

    A non isolated buck regulator requires a high side switch which will be difficult.
    A UC3844 and transformer could be used for a flyback isolated switcher.

    I have used this circuit at low power. T1 and T2 are high voltage transistors and C1 can be added to help with outptu stability.
    As drawn VOUT is 125V

    There is no current limit; an input fuse is a must.

  • 0 in reply to Ron Michallick
    Intellectual 315 points

    Thank You Ron!

    I will try this circuit on Multisim first, and then I will build it. I have Switcher Pro, and I will explore the Fly back Isolated Switcher topography.